Thin films with oriented structures are known in various fields and are useful for a variety of biological, optical and other applications. In the field of nonlinear optics, for example, oriented polymer films with noncentrosymmetric structures are used as waveguiding media for frequency doubling as well as waveguiding media for electro-optic modulators.
In second-order nonlinear optics, the requisite order is achieved in the polymer media by poling the material (which has chromophores with significant dipole moments) in an electric field above the glass transition temperature (T.sub.g) of the material followed by cooling the material in the presence of the field below its T.sub.g to freeze the induced structure so that it is retained. Some materials, on the other hand, such as certain liquid crystal systems, will passively exhibit order without the need for applying an electric field. Also, work has been done in the area of surfactant-like materials and Langmuir-Blodgett films to utilize the inherent properties of substances which will orient themselves due to physical interaction with their surroundings.
Ringsdorf, Kunitake and others have investigated a variety of multibilayer films for use as reverse-osmosis membranes. Typically, such films are made by forming an aqueous dispersion of liposomic structures and casting them on a substrate, taking care to evaporate the water slowly. See, "Cast Multibilayer Films from Polymerizable Lipids", Macromolecules, Vol. 20 (No. 1), pp. 29-33 (1987); "Immobilization of Cast Bilayer films by Co .gamma.-Irradiation and Other Means", Polymer Journal, Vol. 16, No. 7, pp. 583-585. Of particular interest to the present invention is a system disclosed in Polymer Journal, Vol. 16, No. 2, pp. 187-190 (1984) in a paper entitled "Immobilization of Synthetic Bilayer Membranes as Multilayered Polymer Films". In this publication, a bilayer film comprising an azobenzene amphiphile/poly(vinyl alcohol) mixture cast on a cellulose acetate membrane is described.
On the other hand, highly ordered films such as those in accordance with the present invention are useful as optical media which may be used for recording information per se or may be used as layers in stratified volume holographic optical elements such as those described in Optics Letters, Vol. 13, No. 3 P. 189 et. seg.